97,803 research outputs found
Detection Time Distribution for Several Quantum Particles
We address the question of how to compute the probability distribution of the
time at which a detector clicks, in the situation of non-relativistic
quantum particles in a volume in physical space
and detectors placed along the boundary of . We have
recently [http://arxiv.org/abs/1601.03715] argued in favor of a rule for the
1-particle case that involves a Schr\"odinger equation with an absorbing
boundary condition on introduced by Werner; we call this rule
the "absorbing boundary rule." Here, we describe the natural extension of the
absorbing boundary rule to the -particle case. A key element of this
extension is that, upon a detection event, the wave function gets collapsed by
inserting the detected position, at the time of detection, into the wave
function, thus yielding a wave function of particles. We also describe an
extension of the absorbing boundary rule to the case of moving detectors.Comment: 15 pages LaTeX, no figure
First-Matsubara-frequency rule in a Fermi liquid. Part I: Fermionic self-energy
We analyze in detail the fermionic self-energy \Sigma(\omega, T) in a Fermi
liquid (FL) at finite temperature T and frequency \omega. We consider both
canonical FLs -- systems in spatial dimension D >2, where the leading term in
the fermionic self-energy is analytic [the retarded Im\Sigma^R(\omega,T) =
C(\omega^2 +\pi^2 T^2)], and non-canonical FLs in 1<D <2, where the leading
term in Im\Sigma^R(\omega,T) scales as T^D or \omega^D. We relate the \omega^2
+ \pi^2 T^2 form to a special property of the self-energy -"the
first-Matsubara-frequency rule", which stipulates that \Sigma^R(i\pi T,T) in a
canonical FL contains an O(T) but no T^2 term. We show that in any D >1 the
next term after O(T) in \Sigma^R(i\pi T,T) is of order T^D (T^3\ln T in D=3).
This T^D term comes from only forward- and backward scattering, and is
expressed in terms of fully renormalized amplitudes for these processes. The
overall prefactor of the T^D term vanishes in the "local approximation", when
the interaction can be approximated by its value for the initial and final
fermionic states right on the Fermi surface. The local approximation is
justified near a Pomeranchuk instability, even if the vertex corrections are
non-negligible. We show that the strength of the first-Matsubara-frequency rule
is amplified in the local approximation, where it states that not only the T^D
term vanishes but also that \Sigma^R(i\pi T,T) does not contain any terms
beyond O(T). This rule imposes two constraints on the scaling form of the
self-energy: upon replacing \omega by i\pi T, Im\Sigma^R(\omega,T) must vanish
and Re\Sigma^R (\omega, T) must reduce to O(T). These two constraints should be
taken into consideration in extracting scaling forms of \Sigma^R(\omega,T) from
experimental and numerical data.Comment: 22 pages, 3 figure
Polarisation of the omega meson in the pd-->3He+omega reaction at 1360 and 1450 MeV
The tensor polarisation of omega mesons produced in the pd-->3He+omega
reaction has been studied at two energies near threshold. The 3He nuclei were
detected in coincidence with the pi0pi+pi- or pi0gamma decay products of the
omega. In contrast to the case of phi meson production, the omega mesons are
found to be unpolarised. This brings into question the applicability of the
Okubo-Zweig-Iizuka rule when comparing the production of vector mesons in low
energy hadronic reactions.Comment: 11 pages, 4 figure
Observation of decays into vector meson pairs , , and
Decays of to vector meson pairs , and
are observed for the first time using
\psip events accumulated at the BESIII detector at the BEPCII
collider. The branching fractions are measured to be , , and , for , , and ,
respectively. The observation of decays into a pair of vector
mesons , and indicates that the hadron
helicity selection rule is significantly violated in decays. In
addition, the measurement of gives the rate of doubly
OZI-suppressed decay. Branching fractions for and
decays into other vector meson pairs are also measured with improved precision.Comment: 4 pages, 2 figure
Shear viscosity and spin sum rules in strongly interacting Fermi gases
Fermi gases with short-range interactions are ubiquitous in ultracold atomic
systems. In the absence of spin-flipping processes the number of atoms in each
spin species is conserved separately, and we discuss the associated Ward
identities. For contact interactions the spin conductivity spectral function
sigma_s(omega) has universal power-law tails at high frequency. We derive the
spin f-sum rule and show that it is not affected by these tails in d<4
dimensions. Likewise the shear viscosity spectral function eta(omega) has
universal tails; in contrast they modify the viscosity sum rule in a
characteristic way.Comment: 7 pages, published versio
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